Abstract: Viruses influence microbial community structure and biogeochemical cycles in marine environments. Viral attachment to nonhost surfaces could influence host viral infection rates; however, the prevalence of such viral attachment is not investigated quantitatively. We used coastal seawater viral assemblages and, as models, marine vibriophage (SIO-2) and enterobacteriophages (T2 and T4) to investigate their attachment to probable nonhost marine bacteria. We also studied viral attachment to colloids and other abiotic surfaces in seawater. Centrifugation experiments with bacterium-virus mixtures showed substantial viral loss in the supernatant - 2 presumably due to the viral attachment to bacteria. This attachment (0.04 to 24 viruses μm [bacterial surface area]) varied with bacterium-virus combinations. Surprisingly, filtering seawater on 0.2- μm Anodisc or ∼ polycarbonate filters retained 12 to 84% of viruses presumably attached to ≥0.2 - μm -sized particles and/or the filter surface. Enzymatic digestion followed by epifluorescence and atomic force microscopy suggested that 7 to 25% of the total viruses were attached via β -glycosidic linkages. Furthermore, a substantial proportion (7 to 48%) of viruses became attached to model abiotic surfaces (polycarbonate, polypropylene, and glass), and this has significance for laboratory protocols as well as studies of virus ecology in particle-rich marine environments. Substantial attachment of viruses to nonhost surfaces could influence virus-driven biogeochemical cycles and microbial community structure. Importance: Viruses play important roles in altering microbial community structure and biogeochemical cycles in marine environments. Viral attachment to nonhost surfaces can influence host viral infection rates; however, the prevalence of viral attachment to nonhost surfaces and the ratio of attached viruses to total viruses are little known. We used coastal seawater viral assemblages and used marine vibriophage (SIO-2) and enterobacteriophages (T2 and T4) as models to investigate their attachment to abiotic and biotic surfaces in seawater. Viral attachment was observed on several surfaces, such as nonhost bacteria, polymers, filters, cover glasses, and tube surfaces. This study cautions against commonly used protocols that require viral incubation and seawater fractionation. More importantly, these results could influence virus-driven biogeochemical cycles and microbial community structure in the ocean.

Yamashita, Y., Yagi, Y., Ueno, H., Ooki, A., Hirawake, T., 2020. Characterization of the water masses in the shelf region of the Bering and Chukchi seas with fluorescent organic matter. Journal of Geophysical Research: Oceans 124, 7545-7556.

https://doi.org/10.1029/2019JC015476 Pacific water is an important nutrient source for sustaining biological production in the Chukchi Sea, western Arctic Ocean, which is one of the productive regions in the world. Therefore, to understand the impacts of future environmental changes on biological production in the sea, it is crucial to understand the origins, modification processes, and spatiotemporal variations of the water masses from the Bering Sea with changes in nutrient concentrations. To improve water mass analysis in the shelf regions of the Bering and Chukchi Seas, we observed levels of humic-like fluorescent organic matter (FOM ) by using an in situ fluorometer directly H connected to a temperature-salinity sensor during a cruise in the early summer of 2013 and evaluated the potential of FOM as a third parameter of water mass analysis. The levels of FOM were different among H H specific water masses in the region, and FOM seemed to behave semiconservatively in the shelf regions of the H Bering and Chukchi Seas during the early summer of 2013. The distributional pattern of FOM implies that H FOM estimated by the in situ fluorometer has the potential to (1) separate warm water into riverine-affected H Alaskan Coastal Water and historically photobleached summer Bering Basin Water; (2) distinguish the Anadyr Water, which has low FOM levels and high nutrient concentrations, from the Bering Shelf Water; and (3) H determine different formation/modification processes of dense shelf water that contains high nutrient concentrations.

Yang, B., Steiner, M., Schiffbauer, J.D., Selly, T., Wu, X., Zhang, C., Liu, P., 2020. Ultrastructure of Ediacaran cloudinids suggests diverse taphonomic histories and affinities with non-biomineralized annelids. Scientific Reports 10, 535.

https://doi.org/10.1038/s41598-019-56317-x